#!/usr/bin/env node

const Readable = require('stream').Readable;
let c = 'a'.charCodeAt(0);

class MyReadable extends Readable{
  constructor(){
    super();
  }
  _read() {
    rs.push(String.fromCharCode(c++));
    if(c>'z'.charCodeAt(0)) rs.push(null);
  }
}
let rs = new MyReadable();

rs.pipe(process.stdout);
